Electric switch construction



Oct. 18, 1949. w. H. MARTIN 2,485,399

ELECTRIC SWITCH CONSTRUCTION Filed June 10. 1946 2 Sheets-Sheet 1 INVENTOR. WILLIAM H. MARTIN ATTORNE s Oct 18, 1949; w. H. MARTIN ELECTRIC SWITCH CONSTRUCTION v 2 Sheets-Sheet 2 FIG.6.

Filed June 10, 1946 JNVENTOR.

WILLIAM H.MART|N Patented Oct. 18, 1949 UNITED STATES PATENT OFFICE ELECTRIC SWITCH CONSTRUCTION William H. Martin, Grosse Pointe, Mich.

Application June 10, 1946, Serial No. 675,553

6 Claims.

This invention relates generally to electrical contactors and refers more particularly to improvements in roller type switch construction.

In many types of electric circuits embodying transformers or resistance coils it is desirable to provide switch means for selectively connecting the resistances in parallel or in series to vary the output of the circuit. Various different types of switches have been provided in the past for this purpose, but in most instances these switches are of a nature to cause excessive arcing which is objectionable in that the switch contacts soon become burned to such an extent as to render them unserviceable.

One of the principal objects of this invention is to provide a switch capable of being readily operated and constructed in a manner to enable breaking and making the required circuits with the minimum amount of arcing.

Another object of this invention is to provide a switch having a rotatable contact carrying member provided with opposed contact rollers spaced equal distances from the axis of rotation of the member and having a plurality of spaced contact buttons concentrically positioned with respect to the axis of rotation of the member in the path of travel of the rollers for successively engaging the rollers.

Still another feature of this invention is to provide a switch of the above general type wherein the rollers are normally urged in a direction toward the contact buttons and wherein the spacing between the buttons is such that adjacent buttons are successively bridged by the rollers as the contact carrying member is rotated in one directtion.

A further object of this invention is to provide a switch of the above type wherein the contact roller at one end of the carrier is interchangeable with an insulating roller. This construction enables employing the same general construction of switch for selectively connecting varying quantities of resistance in an electric circuit.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a plan view of a switch constructed in accordance with this invention;

Figure 2 is a sectional view taken on the line 22 of Figure 1;

Figure 3 is a wiring diagram showing the switch in one position of adjustment;

Figure 4 is a wiring diagram showing the switch in another position of adjustment;

Figure 5 is a sectional view similar to Figure 2 showing a slightly modified construction; and

Figure 6 is a wiring diagram illustrating the operation of the switch shown in Figure 5.

The switch shown in Figures 1 to 4 inclusive comprises a base plate l0 and a cover II. The plate It] is formed of a dielectric material having an opening I2 at the center and having circumferentially spaced metal inserts l3 anchored in the bottom face of the plate adjacent the periphery of the latter. The cover II is preferably formed of sheet metal and is generally cup-shaped in configuration. The free edge portion of the side wall of the cover is bent outwardly to form an attaching flange l4 adapted to seat on the top surface of the plate I!) and having openings therethrough, respectively, registerable with the inserts 13 to enable securing the attaching flange M to the plate by the screws [5. The top wall of the cover is apertured in alignment with the opening 12 in the plate l0 and a shaft [6 extends through the aligned openings. The lower end of the shaft is journalled in a bushing ll fixed in the opening l2 and the upper end portion of the shaft is journalled in a bushing l8 suitably fixed in the aperture through the top wall of the cover. An operating element 19 in the form of a narrow elongated member is bored intermediate the ends for receiving the upper end of the shaft and is secured to the latter by a tapered pin 20.

A plurality of fixed contact elements 2| are positioned on the top surface of the plate [0 in concentric relation to the axis of the shaft I6 and are spaced circumferentially from each other. Although the number of the contacts will vary in accordance with the particular requirement, the switch shown herein for the purpose of illustration comprises six contacts indicated in Figures 3 and 4 of the drawings by the reference characters 22 to 21 inclusive. These contacts are in the form of studs having shank portions which project through the plate ID and are clamped to the latter by suitable nuts. The heads of the studs are crowned and are formed with spherically shaped contact surfaces 28.

Rotatably supported on the shaft I6 within the cover II is a contact carrying member 29 of dielectric material having a :bore 30 therethrough intermediate the ends for receiving the shaft l6 and having journals 3! at opposite ends thereof. The journals are space equal distances from the shaft l6 and have a common axis which intersects the axis of the shaft l6 at right angles to the latter axis. Contact rollers 32 and 33 are respectively rotatably supported on the journals 3| and are formed of a material having good electrical conducting characteristics. The rollers are so positioned with respect to each other that the peripheral portions thereof successively bridge adjacent contacts upon rotation of the member about the axis of the shaft IS. The peripheral portions of the rollers are fashioned with annular grooves 34 having the base portions curved to correspond substantially to the degree of curvature of the spherically shaped contacting surfaces 28 of the contacts 2|. Thus, the contacting faces of the rollers are fashioned to have an extended area of engagement with the contacting surfaces of the contacts 2| and electric current losses are thereby reduced to a minimum.

In the present instance contact carrying member 29 is rotated as a unit with the shaft I6 by an inverted U-shaped driving bracket 35 having a base portion 36 centrally apertured to receive the shaft I6 and having leg portions 31, respectively, sli'dably engaging opposite sides of the member 29 between the journals 3|. The base 36 of the bracket is welded, brazed or otherwise secured to the shaft l5 so that rotation of the shaft by manipulation of the operator l9 effects a corresponding rotation of the member 29 and contact rollers 32 and 33.

The bore 30 in the member 23 is counter-bored at the upper end to form a, recess 38 for receiving the lower end of a coil spring 33. The spring 39 surrounds the shaft I 6 and is held under compression between the base 36 of the bracket and the bottom wall of the counter-bore. It follows from the above that the spring 39 urges the rollers into frictional contact with the contacts 2| and in effect provides for snapping the rollers into engagement with their respective contacts 2|. As a result, arcs are reduced to a minimum and an intimate electrical connection is assured.

One application of the switch previously described is shown in Figures 3 and 4 of the drawings by way of illustration. In these figures of the drawings the switch is used in combination with two resistors 40 and 4| for selectively con necting the latter in series and in parallel in an electric circuit. In Figure 3 of the drawings the switch is shown in a position wherein the resistors are connected in series and the total effective resistance in the circuit is the sum of the separate resistances. In Figure 4 of the drawings the switch is in a position wherein the re sistors are connected in parallel and the total effective resistance in the circuit is somewhat smaller than either resistance.

Referring more in detail to Figure 3 of the drawings, it will be noted that the lower end of the resistor 40 is electrically connected to the contact 26 which is also electrically connected to L1 and the upper end of the resistor is electrically connected to the contact 23. The lower end of the resistor 4|, on the other hand, is electrically connected to the contact 22 which is permanently connected to the contact 2! by a shunt 42. The upper end of the resistor 4| is electrically connected to the contact 24 which is also connected to L2.

The lines A and B in Figure 3 of the drawings respectively indicate the positions of the contact rollers 32 and 33. As shown, the contact 22 is electrically connected to the contact 23 by the line A (contact roller 32) and the contact 26 is electrically connected to the contact 25 by the line B (contact roller '33). The direction of flow of the electric current is indicated by the arrows in Figure 3 of the drawings and it will be noted 4 that the two resistors are connected in series by the switch.

Rotation of the contact carrying member 23 in a clockwise direction from the position shown in Figure 3 of the drawings causes the contact rollers 32 and 33' to respectively bridge the contacts 23, 24 and 26, 21. This latter position of the rollers is indicated in Figure 4 of the drawings and it will be noted that the electric current divides at the contact 26 and flows through both resistors to the line L2. Thus, the resistors are connected in parallel and the total resistance is inversely proportional to the resistance offered by each resistor.

When the contacts 24 and are bridged by one of the contact rollers and the contacts 22 and 21 are bridged by the other contact roller, the switch is in its off position or, in other words, the circuit is broken. Suitable indicia may be stamped or otherwise applied to the top surface of the switch cover, if desired, to indicate the different positions of the switch.

The switch 43 illustrated in Figure 5 of the drawing is identical to the switch previously described, except for the indicia on the cover and except that one of the contact rollers is replaced by a roller of dielectric material indicated by the reference character 44. Except for the material from which the roller 44 is formed it is exactly the same as the contact rollers. In fact, one of the features of this invention is to enable readily converting the switch shown in Figure 1 of the drawings to the switch illustrated in Figure 5 by merely interchanging the cover for one having the proper indicia and by merely replacing one of the contact rollers with an insulating roller 44.

One of the uses for the switch shown in Figure 5 of the drawings is to selectively connect different numbers of coils of a transformer coil in the circuit to vary the operating characteristics of the latter. In Figure 6 of the drawings the reference character indicates a coil having one end connected to a line L1 and having the opposite end connected to the contact 22 of the switch 43. For the present use of the switch the shunt connector between the contacts 22 and 21 is removed and the contact 23 is permanently electrically connected to the contact 26 by a shunt 46. The contact 26 is also connected to line L2 and the contacts 24 and 25 are respectively connected to intermediate tops of the coil. Remembering that one of the rollers is formed of insulating material it will be noted that when the contacts 22 and 23 are bridged by the contact roller the entire coil is connected in the circuit. On the other hand when the contacts 23 and 24 are bridged by the contact roller approximately two thirds of the coil is connected in the circuit. When the contacts 24 and 25 are bridged by the contact roll the switch is in an off position. However, continued rotation of the contact roll carrying member 29 bridges the contacts 25 and 26 with the contact roller and the amount of the coil connected in the circuit is again reduced.

In the event it is desired to use the two switches in combination, the contact 24 of the switch shown in Figures 1 to 4 of the drawings is electrically connected to the contact 21 of the switch 43 instead of to the line L2 and the upper end of the coil 45 is electrically connected to the contact 2'! instead of to line L1. As in the first described form of the invention, the various positions of the switch 43 may be designated by providing suitable indicia on the cover of this switch.

What I claim as my invention is:

1. An electric switch having a supporting plate, a contact carrying member of insulating material supported at one side of the plate for rotation and having aligned journals spaced equal distances from the axis of rotation of said member, contact rollers respectively rotatably supported on the journals and insulated from each other by said contact carrying member, and a plurality of contacts fixed to the plate in concentric relation to the axis of rotation of the contact carrying member and spaced equal distances from each other in the path of the rollers, said contacts being insulated from each other and the space between the contacts being determined to enable successively bridging adjacent contacts by the rollers during rotation of the contact carrying member about its axis.

2. An electric switch having a supporting plate of insulating material, a shaft journalled on the plate, a contact carrying member of insulating material supported intermediate its ends on the shaft for rotation by the shaft, journals on said member extending radially outwardly with respect to the axis of said shaft, contact rollers respectively rotatably supported on the journals and insulated from each other by said contact carrying member, a plurality of spaced contacts fixed to the plate in concentric relation to the axis of rotation of the contact carrying member, the spacing between adjacent contacts being so determined with respect to the diameter of the rollers that the latter successively bridge adjacent contacts during rotation of the contact carrying member about said shaft, and yieldable means acting on the contact carrying member for urging the rollers in a direction toward said contacts.

3. An electric switch having a supporting plate of insulating material, a shaft supported on the plate for rotation, a contact carrying member of insulating material rotatable as a unit with the shaft and having journals extending radially outwardly with respect to the axis of rotation of the shaft, contact rollers respectively rotatably supported on the journals and insulated from each other by said contact carrying member, a plurality of spaced contacts fixed to the plate in concentric relation to the axis of rotation of the contact carrying member, the spacing between adjacent contacts being so determined with respect to the diameter of the rollers that the latter successively bridge adjacent contacts during rotation of the contact carrying member about said shaft, yieldable means acting on the contact carrying member for urging the rollers in a direction toward said contacts, a housing secured to the plate and having an opening through the top wall through which the shaft projects, and an operating member secured to l the projecting end of the shaft for rotating the shaft.

4. An electric switch having a supporting plate, a plurality of spaced contacts fixed to the plate in concentric relation to a common axis and having spherically shaped heads, and a contact roller having an annular groove in the periphery thereof provided with a base transversely curved to correspond substantially to the curvature of the heads on the contacts, said roller being insulatingly supported for rotation about an axis extending radially from the common axis aforesaid and also supported for rotation about the latter axis to successively bridge the head portions of adjacent contacts.

5. An electric switch having a supporting plate of insulating material, a shaft mounted on the plate for rotation, a plurality of spaced contacts fixed to the plate in concentric relation to the axis of rotation of the shaft and having spherically shaped head portions, a contact carrying member of insulating material rotatable as a unit with the shaft and having journals extending radially outwardly with respect to the axis of rotation of the shaft, contact rollers respectively rotatably supported on the journals in positions to successively bridge adjacent contacts and having transversely curved recesses in the peripheral surfaces thereof adapted to have an extended bearing contact with the spherical headed portions on said contacts.

6. An electric switch having a supporting plate of insulating material, a shaft mounted on the supporting plate for rotation, a plurality of spaced contacts fixed to the plane in concentric relation to the axis of rotation of the shaft, a member of insulating material mounted on the shaft for rotation as a unit with the latter and having journals extending radially outwardly with respect to the axis of rotation of the shaft, a metallic contact roller rotatably supported on one journal in a position to successively bridge adjacent contacts, and a contact roller of insulating material having the same peripheral configuration as said metallic contact roller rotatably supported on another journal, and also positioned to successively bridge adjacent contacts to provide a symmetrical construction.

WILLIAM H. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,410,855 Venera Mar. 28, 1922 FOREIGN PATENTS Number Country Date 97,611 Austria Mar. 15, 1924 99,606 Switzerland June 16, 1923 

